Did I say anything about boot up speed? I'm referring to how cgroup level resource controls can be configured. The follow up discussion in the blog comments about detached screen session behavior in a cgroups controlled login session speak directly to the sorts of tradeoff of the flexibility of the cgroups level controls as it applies to long running services like login sessions.
The design of systemd isn't _just_ about service start up. There are elements in there which deal with resource constraints over the lifetime of the systemd control process via its use of cgroups. I think sysadmins should attempt to wrap their heads around when cgroup level control are going to be useful..and when they are going to be..in the way. Part of that will mean getting familiar with the libcgroup utilities..which are mentioned in the blog story.
To paint systemd as just being a different way to start things up fast is missing a critical point about service management in choosing to rely on cgroups in the design.